The present invention broadly relates to a gear tooth measuring or test feeler for a gear tooth measuring or testing machine and, more specifically, pertains to a new and improved construction of a gear tooth test feeler having a carrier or support member with a deflectable sensing lever.
Generally speaking, the gear tooth measuring or test feeler of the present invention is for a gear tooth measuring or testing machine and comprises a carrier or support member which contains a deflectable sensing lever. The deflectable sensing lever carries a feeler tip on one of its ends and a measurement system on its other end. A pivot bearing means for the sensing lever is fastened to the carrier member and generates a counter-force which increases in proportion to the deflection of the sensing lever.
In other words, the gear tooth test feeler of the present invention is of the type comprising a sensing lever which defines a plane of deflection and has a first end, a second end, a region or intermediate region adjacent to the second end, a first side, a second side opposite to the first side and a central or neutral position as well as a feeler tip mounted on the first end of the sensing lever, a measuring system mounted on the second end of the sensing lever, a carrier or support member, first pivot bearing means for deflectably mounting the sensing lever within the carrier member to perform a deflection substantially in the plane of deflection. The first pivot bearing means is of a construction which generates a counter-force which increases in proportion to the deflection of the sensing lever.
A gear tooth measuring or test feeler of this type is known from the German Pat. No. 2,364,918, published Sept. 2, 1976, and has a cross-spring joint comprising two mutually perpendicularly arranged leaf springs as its pivot bearing means. Only one left hand or only one right hand gear tooth flank at a time can be sensed or tested with this feeler and for this purpose the feeler must be biased or preloaded in a predetermined direction of deflection. A rotatable ring is provided for performing this biasing or preloading which comprises a camming surface defined by a skew plane which acts upon flat springs which press the test feeler into one or another of two terminal positions.
If the gear tooth flank to be measured or tested now presses against the feeler tip in the opposite direction, then the sensing lever is subjected to a pivoting motion within its deflection plane in the direction of a central or neutral position and in opposition to the spring force of one of the two flat springs. This situation is sensed by the measuring system.
Since this known gear tooth measuring or test feeler must be switched manually from operation for testing one handedness of gear tooth flank to operation for testing the other, it cannot be employed in automatic gear tooth measuring or testing machines. While the provision of a remote-controlled drive for the adjustment ring provided for biasing or preloading the flat springs is conceivable, space restrictions preclude it.
With this known test feeler measurements cannot be made commencing from the central or neutral position of the sensing lever since the flat springs and the leaf springs of the cross-spring joint generate a zero force in the neutral position and an increasingly greater force as the angular deflection increases, which varies approximately according to the dash line curve K in the force-displacement diagram of FIG. 1. In order that reproducible measurement or testing results can be achieved at all with this known gear test feeler, the gear test feeler must initially be deflected out of the central or neutral position in one direction or the other with a predetermined degree of biasing or preloading.
The curve K also shows that the contact pressure of the feeler tip of this known gear tooth test feeler is strongly dependent upon the deflection displacement. Measurements with variable contact pressure produce considerable errors, especially with rough gear tooth flank surfaces, if a measurement precision of 1 .mu.m is to be attained. Due to the measurement pressure increasing with increasing deflection, the known gear tooth test feeler can only supply relative values which must be individually interpreted on the basis of calibration curves and the like.
This measurement procedure is unsuitable for automatic gear tooth measuring or testing machines in which the evaluation of the measurement is performed by a computer, since the computer should be supplied with absolute values in as far as possible. This poses the prerequisite that measurement be performed throughout the entire measurement region with as nearly as possible the same measurement pressure, which is not possible with this known gear tooth test feeler for the reasons discussed above.
Furthermore, a well-defined central or neutral position is also not readily attainable with this known gear tooth test feeler, since the terminal positions of its sensing lever are determined by elastic stop members.